U.S. Pat. No. 9,278,435 is one previous invention of the present inventors', which discloses and comprises a mounting seat 10, a driving shaft 20, four pawls 30, four springs 40, a fixing ring 50, a control member 60, a bead 70, a positioning spring 71, a C-clip 80 and a clipping member 81. The rear side of the mounting seat 10 is connected with a handle (not shown) and has a space 11 defined in the front side thereof. Two first slot 112 and two second slots 113 are defined in the inside of the space 11. Each of the first slots 111 has a first hole 112 and each of the second slots 113 has a second hole 114. A passage 12 is defined through the mounting seat 10 and has a smaller diameter. A reception hole 13 is defined in the wall of the mounting seat 10. The mounting seat 10 has two fixing members 14 and four fixing slots 15 defined in the front side thereof. A block 16 extends from the outside of the mounting seat 10 and located in opposite to the reception hole 13. The driving shaft 20 has a ratchet portion 21 with multiple teeth. A section 22 extends from the rear end of the driving shaft 20 and is rotatably inserted through the passage 12. A working end 24 of the driving shaft 20 has a polygonal recess to be connected with a driving member. Four pawls 30 are respectively located in the first and second slots 111, 113, and each pawl 30 has a bottom insertion 31 and a top insertion 32 extending from two ends of one side thereof. The bottom insertions 31 of the pawls 30 in the first slots 111 and second slots 113 are pivotably inserted into the first holes 112 and second holes 114 respectively so that each of the pawls 30 is pivotable to engage one of the concavities of the ratchet portion 21. Therefore, the driving shaft 20 is driven to rotate counter clockwise or clockwise by rotating the mounting seat 10 by the engagement between the pawls 30 in the first slots 111 or second slots 113 and the ratchet portion 21. Four springs 40 provide a force to pivot the pawls 30 respectively to engage with the ratchet portion 21. By the force from the springs 40, the four pawls 30 are pivoted and engaged with the concavities of the ratchet portion 21. When the driving shaft 20 is rotated counter clockwise or clockwise, the teeth of the ratchet portion 21 drive the pawls 30 in the first slots 111 or second slots 113 to compress the springs 40 on respective insides of the pawls 30 so that the driving shaft 20 is freely rotated. The fixing ring 50 is a ring-shaped member and is connected to the front side of the mounting seat 10, and has four through holes 51, two apertures 52 and four protrusions 53. The top insertions 32 of the four pawls 30 are pivotably inserted into the four through holes 51. The two fixing members 14 are inserted into the two apertures 52. The four protrusions 53 are engaged with the four fixing slots 15. The control member 60 is rotatably mounted to the mounting seat 10 and has a mounting hole 61 for the driving shaft 20 rotatably extending through. Two control plates 62 symmetrically extend from the inner periphery of the mounting hole 61. When the control member 60 is rotated clockwise or clockwise, the control plates 62 pivot the two pawls 30 in the second slots 113 or first slots 111 to compress the springs 40 and remove the two pawls 30 from the concavities of the ratchet portion 21, so that the driving shaft 20 is freely rotated counter clockwise or clockwise relative to the mounting seat 10. The C-clip 80 and clipping member 81 are engaged with the groove 23 and annular slot 25 of the driving shaft 20 respectively to restrict the control member 60 from being separated from the front side of the mounting seat 10.
The disadvantages of the above-mentioned previous patent are: 1) the two pawls 30 are pivoted in the first slots 111 and second slots 113 by bottom insertion 31 and top insertion 32 inserting in the first hole 112 and second hole 114 respectively so as to be pivotable to engage with the ratchet portion 21, but the pawl 30 only use their distal ends to engage one concavity between two teeth of the ratchet portion 21, so the drive torque is very lower; and 2) the bottom insertion 31 and top insertion 32 of the pawls 30 are in plate shape, so that they are unstable when insert in the first hole 112 and second hole 114.
The present invention intends to provide a ratchet driving device for a ratchet screwdriver to improve the shortcomings of the prior arts mentioned above.